Yes, the Storm pea is a little subtle.
Your results aren't necessarily in conflict with theirs.

They were in a heavily forested environment, which they said reduced the whistle range considerably from what it was over clear land, and seemed (based on my quick frequency testing) to favor lower pitched noise.

I would expect the Storm to outdistance the yell/scream over clear land, based on the 2008 whistle test dB results, at least.

There are lots of other variables with the human voice (and the whistle, for that matter): timbre, volume, listener hearing loss (both permanent, and temporary from whistle testing).

In any event, the NZ folks were recommending a whistle, not a yell. They didn't state why, but the classic reason is that your voice wears out very quickly with loud yelling.

From my summary of the 2008 Part 2 whistle test report:

"One contender in the 2008 Pt 2 test was an adult human yell: 110 dB try 1, 107 dB try 2, 104 dB try three - affected voice, larygnitis next morning. Get a whistle!"

(In a separate post, that tester (Kevin) mentioned having laryngitis for two days afterwards).